﻿<p><em>IfcProjectedCRS</em> is a coordinate reference system of the map to which the map translation of the local engineering coordinate system of the construction or
facility engineering project relates. The <em>MapProjection</em> and <em>MapZone</em> attributes uniquely identify the projection to the underlying geographic
coordinate reference system, provided that they are well-known in the receiving application. The projected coordinate reference system is assumed to be a 2D or 3D right-handed Cartesian coordinate system, the optional <em>MapUnit</em> attribute can be used determine the
length unit used by the map.</p>

<blockquote class="extDef">NOTE&nbsp; Definition from OpenGIS Abstract Specification, Topic 2:<br> 
A 2D (or with vertical coordinate axis 3D) coordinate reference system used to approximate the shape of the earth on a planar surface, but in such a way that the distortion that is inherent to the approximation is carefully controlled and known. Distortion correction is commonly applied to calculated bearings and distances to produce values that are a close match to actual field values.
</blockquote>

<p>The unambiguous identifier by which the coordinate reference system is know, is stored in the inherited <em>Name</em> attribute. Well defined identifiers include the map projection and also the map zone information. In these cases the <em>MapProjection</em> and the <em>MapZone</em> attributes can be omitted.</p>

<blockquote class="example">
EXAMPLE&nbsp; The identifier 'EPSG:25832' defines the map projection 'UTM' and the zone '32N' in additon to the geodetic and vertical datum.
</blockquote>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC4.
</blockquote>